This invention relates to rotary drilling heads for earth boring apparatus, and more particularly, to remotely controlled clamps with a driving variable torque motor for connecting to the drilling head body a part of the drilling head to be removed through a rotary table.
In conventional drilling by the rotary method, a drilling head surmounts the stack of drilling equipment for permitting the drilling fluid in the well to exit the annulus around the drill string and for sealing between the upper end of the drilling stack and the rotating drill string extending therethrough and down into the well. A typical drilling head includes a tubular body having a side outlet for exiting the drilling fluid and a bottom flange for connection to a blowout preventer or other drilling stack member. The drilling head also includes a seal between the body of the drilling head and the kelly or top joint forming the drive for the drill string.
A typical drilling head assembly includes a main housing having an upper stationary housing rigidly affixed to the main housing by a split clamp assembly encircling outwardly directed flanges disposed on the upper stationary and main housings. The main housing has a lower flange for connection to the borehole casting and an integral outlet port to conduct fluid flow from the borehole annulus. The upper stationary housing rotatably receives a rotating bowl with roller bearings therebetween. Seals are provided to prevent contamination of the roller bearings. A stripper is affixed to the lower end of the rotating bowl and includes a rotating seal member to sealingly engage the main housing above the outlet port and an interior sealing surface for sealingly engaging the kelly or drive tube extending through the drilling head. A threaded nut is provided to retain the rotating bowl within the upper stationary housing.
The drilling head is located just below the rotary table. The rotary table has an aperture for the master bushing which in turn has an aperture for the drive bushing which rotates the kelly or drive tube. The drive bushing also has an aperture which will not pass over the connector joint at the lower end of the kelly. When it is necessary to elevate the kelly out of the drilling head, as when adding a joint of drill pipe or when removing the drill string from the well bore to change the drill bit, the drive bushing lifts out of the aperture in the master bushing and the kelly connector then passes up through the rotary table.
During installation or possibly during operation, it is necessary to remove a portion, such as the rotating bowl and/or upper stationary housing, or all of the drilling head from underneath the rotary table. Rotary heads, such as that disclosed in U.S. Pat. No. 4,285,406 entitled "Drilling Head," are dimensioned to permit the removal of the drilling head through the aperture in the rotary table upon disconnection of the side outlet.
The rotating bowl and upper stationary housing of the drilling head may be removed by unclamping the flanges on the upper stationary and main housings. It is preferred that such clamp be disengaged from a remote position above the rotary table. Such a clamp and hydraulic motor are disclosed in the above mentioned U.S. Pat. No. 4,285,406.
Another type of clamp and clamp opening and closing device is disclosed in U.S. Pat. No. 3,661,409 to Brown et al. The Brown clamp comprises a plurality of arcuate segments having wedging surfaces for engaging corresponding flanges on the mating apparatus to be connected. The ends of the clamp are connected to a clamp opening and closing device. Other than at the ends of the clamp, the adjacent arcuate segments are hinged to one another at the top and bottom by clamp hinges in the form of elongated rigid links.
The Brown clamp opening and closing device includes a drive screw having two axially spaced portions which are helically threaded in an opposite sense from one another and a cranking portion of non-circular section for receipt of an air motor chuck, hydraulic motor chuck, hand crank, or the like for rotating the drive screw about its longitudinal axis. Received on threaded portions of the drive screw in driven relationship thereto are trunnions which include vertically upwardly and vertically downwardly extending stub axle pins. Four elongated rigid links connect the two near hinge pins at the ends of the clamp to the respective trunnions so that rotation of the drive screw in a first sense will generally radially contract the clamp by transmission of force through the links, pins and segments and so that rotation of the drive screw in a second, opposite sense will generally radially expand the clamp.
In operation, the drive screw of the Brown clamp is rotated clockwise which will draw the two trunnions circumferentially together, since a left and right hand threaded arrangement is provided on these units. As the clamp begins to circumferentially draw together, camming guide slots control the movement of the clamp segments whereby the back of the clamping unit is brought into contact with the flanges first. The clamping segments along the sides of the unit are drawn initially forward toward the drive unit and then are allowed to engage the hub segments after the back segment has become partially engaged. To open the unit, the drive screws are then turned counterclockwise at which time the trunnions begin to circumferentially separate. As the front clamp segments move outward and contact the retaining can, an external camming force, causing tangential circumferential loads to be applied to the remaining segments, sequentially forces the remaining clamp segments off the flange tapers. In the full open position, all of the clamp segments are wedged back against the inside of the retaining can and the clamp is centered around the flange O.D. The top apparatus may then be removed.
Because drilling heads are located in an almost inaccessible location under the rotary drilling table, and because the clamp segments and drive screw tend to corrode and freeze, it is almost imperative that the clamp be opened by motor driven mechanical means rather than manually. Although the prior art teaches the use of air and hydraulic motors, such hydraulic motors emit a constant torque and without impacting the nut and screw. Often such prior art motors are unable to break open the clamp due to the corrosion inherent at the drilling location.
Impact wrenches are well known for use in tightening or loosening threaded fasteners, such as bolts and nuts. One type of impact wrench is disclosed in U.S. Pat. No. 3,414,066. The wrench includes a housing in which is supported a pneumatically powered motor of the conventional slidable blade type with a driving shaft. The motor has a splined driving connection between the shaft and a rotatable hammer. The hammer is bearing supported within the housing and is retained against axial movement. The hammer has another splined driving connection with a rotatable impacting dog. The dog has a normal retracted position and on its forward face anvil impacting jaws. During operation the dog is periodically advanced axially on the splined connection by cams into impacting relation with an anvil. The anvil is journaled for rotation in the nose of the housing and has an external shank end for driving connection with a work socket. The socket is suited for drivingly engaging work, which may be a bolt head, nut, or other threaded fastener. A repetitive impact action occurs upon revolution of the dog relative to the cam and anvil so that the impact is repeated upon every revolution of the dog.
It is desirable to have the ability to remove and replace the top closure member of a drilling head without going below the rig floor to dismantle the drilling head and slip it out from underneath the rig floor. The top closure member includes the rotating portion and upper stationary portion of the drilling head. To avoid this problem, it is necessary that the top closure member of the drilling head be easily removable from the drilling head and dimensioned so as to pass through the apertures in the rotary table. Further, it is desirable not to have to disconnect lubrication lines for lubricating the rotating parts of the drilling head prior to removing the top closure member.
As shown in the prior art, the top closure member is generally connected to the body of the drilling head by a clamp. It defeats the object of avoiding going below the rig floor if the clamp cannot be activated remotely such as from above the rig floor. Manual and motor drive mechanisms have been unsuccessful in the prior art where the clamp segments and/or drive screws have corroded and frozen, preventing their activation. The present invention provides such desirable features as a removable drive bushing, removable rotor, removable stator and a removable side outlet, all of which will pass through the master bushing opening of a standard rotary drilling table, and a clamp and clamp opening and closing device driven by an impacting variable torque motor which will permit an impacting torque to break open the clamp and a lesser constant torque for the continued opening of the clamp.
Other objects and advantages of the invention will appear from the following description thereof.